Shinnosuke Tsuji (辻新之助, Tsuji Shinnosuke), nicknamed "Mop Head" by Kenichi, first appears in Battle 24 as an ambitious rival of Kisara's, often getting into arguments with other members about who was stronger. Though he has few techniques, his fighting experience without any particular fighting style more than made up for it during their first fight.

Tsuji had hoped to one day lead a gang stronger than Ragnarok but his dreams were crushed by Kenichi. He initially had hordes of men as followers, but after he was beaten by Kenichi's unintentional sneak attack, he lost all but two of them. Tsuji was angry at Kenichi at first, but calmed down when his two remaining followers stated that they stuck by him because he was their friend. He grows a bit of respect for Kenichi, informing him of Takeda's impending punishment at the hands of Ragnarok and warning him of Hermit.

Tsuji, upon entering Ryozanpaku to face Kenichi, also harbored a slight attraction for Miu.

An ambitious Tsuji Shinnosuke leads a small gang over to fight Kenichi, asking him to join Ragnarok. He becomes irritated by Kenichi's denial and continual upholdings of logical thought and manages to defeat him with his pure fighting experience. He seems dissapointed by kenichi barely managing to prove himself, apart from taking a good beating.

Tsuji Threatening kenichi

When Kenichi finally manages to get Tsuji off balance, he is too amazed by this accomplishment that he forgets about the fight, leading Tsuji to take over and threatens to break Kenichi's leg if he does not join him. Takeda shows up and manages to save the day. He then orders his goons to chase Kenichi after the latter is rescued by Takeda, but is stopped by Ma Kensei.

Tsuji, with his small gang, walks around a corner, where Kenichi accidentally kicks him and knocks him down, resulting in a loss. The loss happens a third time, and Tsuji starts to respect Kenichi when he realizes that the two members who stuck by his side were his friends.

Following his defeat by Kenichi, Tsuji goes into the mountains to train. He finds a master, a large old man wearing a bear skin over his head that stretched down to his legs who decided to teach Tsuji his martial arts under the condition that Tsuji has to leave the mountains when he finishes his training.

Tsuji comes back from his training in the mountains to return to Ragnarok, and immediately heads over to Kisara's headquarters to challenge her. However, he is more than surprised to find out that Ragnarok has disbanded and Shinpaku Alliance now holds it. Losing the initial purpose of his training, he decides to seek out Kenichi again to defeat him in a rematch.

While he fights Kenichi in Ryozanpaku, Tsuji demonstrates a tremendous increase in skill, though his punches are still slow enough for Kenichi to dodge. Nonetheless, he was able to obtain a victory over Kenichi, ironically by means of an opportune attack when Kenichi looked away, similar to how he was defeated by Kenichi. He then runs away refusing a rematch saying that he's going to hold onto the victory for the rest of his life and never fight Kenichi again.

Tsuji is last seen in the epilogue performing in a band composed of Siegfried, Thor, and himself.

Before learning Koppou, Tsuji's fighting style was basically a mix of reckless street fighting, instinct, and experience. Tsuji's original fighting style was reckless, had little to no technique, and overall left a lot of openings when he fought, but because of his experience in fighting in the streets and being in a gang, Tsuji more than makes up for these shortcomings by using straight foreword and dirty tactics to stay unpredicable and relentless when fighting, which combined with his experence makes him a strong fighter. Since Ragnarok's dispansion, Tsuji has learned from a master-class fighter and become a practisioner of the martial art style of Koppou. According to Kōetsuji, the style Tsuji uses is possibly over a thousand years old and is one of the oldest Japanese styles of Kenpou and revolved around the kanji, which means talent or skill to understand a clever technique in little time in contemporary Japanese and "core" in ancient Japanese. For practitioners, the difference between those who knew the "core" and those who didn't was in their understanding. Tsuji's way of Koppou was a little different from how it is used in regular styles.